An infestation of bed bugs can be confirmed by finding physical evidence, with the most definitive sign often being the presence of egg casings. Bed bug egg casings are the empty, translucent shells left behind after a first-stage nymph successfully hatches. Identifying these remnants reliably determines if a current or past infestation has taken hold in a living space. Recognizing these tiny casings confirms that bed bugs have been actively breeding and developing in the immediate area.
Appearance of the Bed Bug Egg Casing
Bed bug egg casings are extremely small, measuring about 1 millimeter in length, comparable to the size of a pinhead or a grain of salt. They have an elongated, oval shape, often described as resembling a miniature grain of rice. The color of a hatched casing is typically pearly white or translucent, sometimes appearing slightly duller than a freshly laid, unhatched egg.
When a female bed bug lays an egg, she coats it with a sticky, glue-like substance that strongly adheres it to a surface. This adhesive causes the casing to remain firmly attached even after the nymph has emerged, making them a lasting sign of activity. The texture of the empty casing is dry and hard.
The distinguishing feature that confirms a particle is a hatched casing is the visible opening at one end. Bed bug eggs possess a small, hinged cap that the nymph pushes open to exit the shell. When examining a casing under magnification, this missing or opened cap confirms the shell is empty and the nymph has emerged.
Common Hiding Spots for Casings
Because the eggs are laid with a sticky coating, the resulting casings are often found in tight, protected harborages close to where the host sleeps. Casings frequently accumulate in clusters within the seams, tufts, and piping of mattresses and box springs.
The casings are also commonly found nestled in crevices and joints of the bed frame and headboard. Bed bugs prefer to lay their eggs in spaces no wider than the thickness of a credit card, including cracks in baseboards and behind peeling wallpaper. In more severe infestations, casings may even be found in less obvious places like electrical outlets or behind wall-mounted pictures.
Differentiating Casings from Other Infestation Signs
It is important to distinguish the tiny white egg casings from the other debris left behind by bed bugs, such as fecal spots and shed skins. Fecal spots, or droppings, are dark brown or black specks that look like tiny felt-tip pen marks. Unlike the three-dimensional, oval egg casings, these spots are flat and will often bleed out like ink when wiped with a damp cloth.
Shed skins, also known as exuviae, are the hollow exoskeletons left by nymphs during development. These skins are larger than egg casings, retaining the general shape of the bug, and can range up to the size of an adult bed bug. They are typically pale, translucent, and yellowish-brown, which contrasts with the pearly white color of the smaller egg casing.